1. School of Software, Dalian Jiaotong University, Dalian 116028, China
2. School of Electronic and Information Engineering, Beijing Jiaotong University, Beijing 100044, China
3. School of Computer Science, China West Normal University, Nanchong 637002, China
4. College of Electronic Information and Automation, Civil Aviation University of China, Tianjin 300300, China
5. State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031, China